Immunologists have known for decades that immunity is the result of the various contributions of cell-mediated and antibody-mediated responses. Within recent years the dichotomy of possible immune responses has been further defined by the knowledge that T helper cells can adopt one of two polar types of reactivity: T helper 1 (Th1) and T helper 2 (Th2). These counter responses can be differentiated by differences in the phenotype of cytokines (Th1, IFNgamma; Th2, IL4, IL10) and isotypes of antibodies (Th1: IgG2a; Th2: IgG1, IgE) they make. Th1 responses are associated with inflammation, while Th2 responses are associated with inflammation, while Th2 responses associated with hypersensitivity and protection against parasitic invasion. Because these two polar responses cross regulate each other it is possible that Th2 responses might be important in the prevention of inflammation in various organs including the eye. Apparently, in the health eye, it is very difficult to induce a Th1 response because of an unusual local regulatory mechanism in the anterior chamber. This research proposal will study the ocular regulatory mechanism known as Anterior Chamber Associated Immune Deviation (ACAID). ACAID is relevant to the up-regulation of Th2 responses and the down regulation of Th1 responses, i.e. inflammation, thereby preserving sight. In an animal model antigenic materials that are placed in the anterior chamber (a.c.) Of the eye evoke a systemic immune response that is distinctly unusual in there is a selective deficiency of delayed-type hypersensitivity (DTH, an indicator of a Th1, response). While this model is well studied, no one has looked at early mechanisms that might be invoked to produce and maintain an ocular Th2 response. We propose that two distinct subpopulations of lymphocytes expressing natural killer (NK) antigens may participate in the early regulation of the polar responses to antigens inoculated into the anterior chamber. Recent data from our laboratory show that ACID does not develop in CD1 deficient mice. This application will exploit this observation by studying the mechanisms and interaction of NKT cells and CD1. We will use a variety of methods to test the hypotheses including flow cytometry with simultaneous labeling of intracellular cytokines and surface markers, morphological analysis of cells in tissues and suspension, molecular biology techniques, including Rnase protection assay. In addition we will evaluate the role of NK antigen positive lymphocytes in whole animal models that are manipulated to prevent ACID and compare ACAID in naive and primed mice. Resents of the studies will generate new information toward understanding the cellular mechanisms of immune deviation in the eye and new insights into the interactions of NKT (innate immunity) and the adaptive immune response.